When a printed panel fails a tape test, the ink is rarely the problem. In almost every case the fault sits in the surface preparation – and all four common causes are avoidable.
Glass gives ink nothing to hold on to
UV inkjet ink is organic. Glass and ceramic are inorganic. Put one on the other and there is no chemical bond available – the cured ink film sits on the surface held only by whatever mechanical grip the substrate happens to offer, which on smooth float glass is close to none.
That is why prints can look perfect coming off the flatbed and still fail a cross-cut test an hour later, or lift at the edges after the panel is cleaned. Nothing degraded. The bond was never there.
An adhesion promoter fixes this by sitting in the interphase region – between the ink and the substrate – where it chemically reacts with the glass and creates molecular bonding points for the organic ink to attach to. It also improves how well the substrate wets with the ink. N-Bond works this way, and because the layer is nano-scale it stays completely invisible.
Mistake 1 – Cleaning that leaves chemistry behind
Standard window cleaner leaves surfactants and additives on the glass. Those residues sit exactly where the primer needs to react, and they block it.
The manufacturer’s procedure is specific: remove dust with a dry cloth, then clean the glass with Cl 50, or with a mixture of isopropyl alcohol and demineralised water at no more than 50/50. A higher water content is actually preferred. Wipe dry with a lint-free paper cloth.
If you have already used an ordinary glass cleaner, always follow it with the IPA-and-water mix. That second pass is what removes and neutralises the chemicals the cleaner left behind.
Mistake 2 – Laying the primer down as a wet film
This is the most common error, and it is counter-intuitive: more primer gives you worse adhesion, not better. N-Bond has to be applied as thin as physically possible – a monolayer, never a wet film. Only that very thin layer produces the best and most consistent results.
Apply with a lint-free non-woven cloth in circular, overlapping motions, then polish off with the application cloth. A trigger spray with a non-woven lint-free cloth works equally well. Cover the whole area.
Clouding is your gauge. If haze appears after drying, you applied too much – reduce the amount on the next panel. The clouding itself is normal and polishes off with a dry, lint-free cotton cloth after one to two minutes. Check again just before printing, because it can reappear.
Before the print run starts the glass should be completely clear, with no visible primer residue. N-Bond does not cloud or discolour glass on its own – visible haze always means excess product.
Mistake 3 – Printing too soon
The primer needs a minimum of 10 minutes to cure before you print. Under standard conditions – 20 °C and 50 % relative humidity – it dries within that window. Tempered glass and glazed ceramic may need longer.
There is a second, less obvious timescale. Depending on substrate, temperature, printer system and ink composition, the full chemical bond can take up to 24 hours to complete. A panel that passes a tape test immediately may not represent the final bond strength, and one that looks marginal at 10 minutes can be sound the next day.
The reaction consumes water molecules, drawn either from the substrate or from the surrounding air. If a test run shows low adhesion, the first thing to extend is the curing time.
At the other end, the primer can be applied up to 24 hours before printing. Printing earlier is still better – a primed panel left waiting collects contamination and settling dust.
Mistake 4 – Priming a hot panel
Apply between +5 °C and +35 °C, and avoid extremely hot surfaces. On a hot panel the solvent flashes off before the primer can level, which leaves excess product behind and produces exactly the clouding described above. Glass coming off a line or sitting in direct sun should be allowed to come back to room temperature first.
Prove adhesion before you commit a run
The cross-cut test is quick, repeatable and the standard first check – score a lattice through the cured ink, apply and remove tape, and inspect. On glass printed with standard UV ink and primed correctly, the manufacturer reports 0 % flaking.
Where the print has to survive real conditions, the same product has been evaluated against harder tests:
- two-hour boiling water immersion
- 24-hour cold water immersion
- glass break test – adhesion checked in the break zone
- ASTM D870, Standard Practice for Testing Water Resistance of Coatings
On anything other than glass or ceramic, test first. Acrylic, certain metals and composites are all workable, but the manufacturer explicitly recommends trials. Never commit a production run on an untested substrate.
The numbers worth keeping on the wall
| Cure before printing | min. 10 minutes |
| Maximum time between priming and printing | 24 hours |
| Full chemical bond | up to 24 hours |
| Consumption | approx. 2.5–5 ml/m² |
| Coverage on glass and ceramic | up to 320 m²/litre |
| Application temperature | +5 to +35 °C |
| Storage temperature | not below 4 °C |
| Shelf life, sealed | 36 months |
| Composition | single component, ready to use |
| Solvents | isopropanol / ethyl alcohol |
| Flash point | 21 °C |
Coverage figures are a guideline and vary with substrate, surface structure and application temperature.
Safety. N-Bond is a flammable liquid and vapour with a flash point of 21 °C. Apply in a well-ventilated area, keep it away from sources of ignition, and use appropriate personal protective equipment. Read the safety directions on the packaging and the Safety Data Sheet before use.
Where this comes from
N-Bond has been in production use since 2014, in print shops across 80 countries, with more than 12 million square metres primed to date. It was developed with suppliers from the glass and printing industries and tested with Canon Production Printing, Roland and Agfa.
It scales down to spray-and-wipe on a single panel and up to roller coaters on a production line – and because the adhesion promoter is on the glass rather than in the ink, your ink keeps its normal shelf life.